Proving a concept: An in vitro approach 1

In vitro techniques to predict the feeding value of feedstuffs should be quick, accurate, and cheap. A 2-step in vitro assay to simulate gastric and intestinal digestion was shown to predict AME value for roosters fairly accurately in cereals, cereal by-products, and oil. In general, in vitro techniques are optimized to estimate the maximum nutrient digestibility, using adult roosters for calibration. Prediction of absolute feeding values of feedstuffs by in vitro assays can be highly erroneous, and techniques describing the rate of degradation (dynamics of digestion) seem more promising than such end-point titrations. Moreover, the value of adult roosters as models for meat- or egg-producing birds is questionable. Although, dynamic in vitro assays and near infrared reflectance look to be promising tools, large data sets are required to improve the validity of these in vitro predictions. Such assays will certainly be helpful to correct tabulated feeding values when deviant feedstuff batches are being used.